Police signal system



Aug. 1, 1933- G. F. c. BAUER POLICE SIGNAL SYSTEM Filed Sept. 18, 1931 TIP LINE COMMON RELAY gmm 2 '@am/ W and 622 1! 1. P o o fi k e m 202200 0 m 1 mm m N S 8N. n w my M w w Wm w/ W i? Z ucR 4, z z a 0 V 3 6 Z l 0 m F? W i a z w ZOZZOO .n, ZOYZOO 202200 202200 Patented Aug. 1, 1933 UNETED STATES r rear POLICE SIGNAL SYSTEll/i Application September 18, 1931 Serial No. 563,501

Claims.

This invention relates to an electrical signalling system and more particularly to a system of this character for use between a central station and a plurality of substations for police purposes.

This application is of the same general type as that described in my co-pending application, Serial No. 525,471, filed March 26, 1931 and the advantages set forth in said application, particularly with reference to the use of an ionized gas type lamp as a visual target at each box, are obtained in the present application.

The present application is, however, greatly simplified as compared with said (so-pending application and is particularly adapted for use in small communities where the cost of installation and maintenance must be very low.

Such police signal systems include a plurality of telephone circuits between a central station switch board and a plurality of police boxes or substations, so that a telephone conversation can be carried on between the central station and any of the substations, and means for giving F either a periodic audible or a periodic visual signal from the central station at any or all of the substations so as to call the nearby officer to the substation or police box for the purpose of giving him instructions.

One of the objects of the present invention is to simplify the equipment as much as possible by eliminating the usual line jacks and interconnecting cords and plugs in installations for smaller communities. In police signal work, as distinguished from standard telephone practice, the telephone calls originate either at the switch board or at one of the police boxes and the switch board is merely a terminal point and not a switching point. This is particularly true in police signal installations where only one switch board is used to cover an entire community. Hence by eliminating the necessary jacks, cords and plugs in smaller community installations the equipment provides full police signal service without the extra cost and upkeep which this extra equipment entails.

In my said co-pending application, Serial No. 525,471, filed March 26, 1931, the switch board equipment consists of a pair of signal lamps and a signal key associated with each line circuit. Inaddition to this there was also an individual line relay for each line. In the present circuit in order to simplify and provide economy of 'construction a visual line signal is used in place of the line lamp in the previous application. This makes it possible to dispense with the individual line relays and in their place use only only one relay, commoning all of the line circuits through this relay. This eliminates the duplication of the circuits associated with the contacts of the line relay.

In said previous application, also, the signal key contained two groups of springs, one group of two springs for operating the line signals and one group of six springs, two of which latter were used for cutting oil the line lamp and the other four for connecting the operators talking set with the line. In the present application this line key has only two groups of two springs each, one group, as in the previous application, for operating the line signals and the other group for connecting the operators circuit to the line. In the said previous application when a group of signals were in operation and the oificer answered from any one of the police boxes he would shut ofi the signals on that line only, the signals on the remaining lines still continuing to function. In the present circuit due to the use of only one common relay on all of the lines, as soon as any party answers, the signals on all the lines stop functioning until the circuit has been restored to its normal condition when the signals automatically continue to operate on the other circuits.

In the present circuit a number of contacts and apparatus necessary to the circuit described in said co-pending application have been eliminated. While the present circuit is not so flexible, in some respects as the other type, for smaller units it is equally as eflicient and has the advantage of lower installation cost and lower maintenance. The installation cost is reduced not only by the elimination of the apparatus reierred to but also because the circuit will operate on a much smaller battery out-put under full load. In the previous circuit whensignals were set up the telltale light was operated on each circuit. 7 This telltale light and the signal control relay required sufficient battery so that in a system of forty to fifty lines the energy consumption was so high that a relatively large sized battery was required to offset the intermittent voltage drops that come on during the flashing periods when the max mum current is being used. In the present circuit this extra strain is eliminated and inasmuch as the single part or" the circuit cannot function during the period that conversation is being carried on over any one line, the voltage drop during operating conditions as above described does not exist. With the present circuit, therefore, the arrangement is such that it is possible to dispense with storage batteries entirely and to use in their place a rectifier giving a filtered current sufficient for one talking circuit only and an unfiltered or partially filtered rectified current for operation of he signal control relays. This will permit the use of a relatively low cost rectifier, thereby eliminating the maintenance and upkeep of a storage battery plant and its associated charging equipment.

Still further objects are to provide switch board equipment which can be made extremely compact, which is reliable and efiicient in its operation and will not readily get out of or er and in which there is a minimum chance of confusion in the operation of the central switch board.

In the accompanying drawing:

Figure 1 is a diagrammatic representation of a police signal circuit arranged according to the present invention.

Figure 2 is a simplified diagrammatic representation of the talking circuit alone.

In standard police signal systems now in use the practice has been to employ a combination of a grounded lamp as a visual signal and a horn or howler across the telephone circuit as an aduible signal. It has heretofore also been the standard practice to employ a tungsten filament lamp Such a lamp has several peculiar characteristics. Its cold resistance is approximately one-seventh its hot resistance and it also gives a white light, a red or other distinctively colored light being necessary for police signal work. If such a tungsten filament lamp were used across the telephone circuit, it was necessary to block the tel phone current from this part of the circuit. Such an organization required a relatively large condenser making an electrical combination, particularly in view of the cold resistance of the lamp, too low for efficient telephone service in as much as this path was a drain on the talki current across this part of the line. Therefore it has been heretofore necessary in standard sys"- tems to use the horn and its condenser across the line, taking advantage of the high impedance of the horn to prevent by-passing of the talking current. However, in standard circuits, the horn across the circuit gave a disagreeable elfect which required additional apparatus at the central station to eliminate. Inasmuch as the horn was flashed on and oil? there developed at the cutting off point a high inductive surge caused by the necessarily large capacity of the condensers used and this surge had to be drained off of the line before the circuit was reestablished to its normal condition. If these high inductive surges were not drained ofi, they created a continual slap of the line relays affecting their permanent adjustment and they also accidentally operated accessory equipment.

The desirable method of operation would be the lamp and condenser across line but the results were uncertain because of the low voltage by-pass which this or ss circuit offered and also since the condenser was more or less abnormally large it reduced the lamp voltage to a large extent.

Another difiiculty resulting from the use of a tungsten filament lamp was that the lamp generally employed used 15 watts of energy but when enclosed in a red globe to give a distinctive signal visible both at day. and at night, the red globe filtered out of the light energy of the lamp leaving only about 3 watts of light energy available ior signalling purposes. Moreover, the blocking of the light through the accumulation of dirt under these circumstances was intensified considerably because there were three surfaces on which dirt could collect; the in and outside of the red globe and the outside of he lamp.

The important diiliculty for smaller community equipment, however, was that as a 15 watt lamp was the smallest practical size to use, the horn used as an audible signal was also developed to operate on the same wattage. From an operating standpoint the energy consumption of both the lamp and the horn made it necessary to use a relatively sized line conductor so that reasonably long distances could be efficiently covered. As these distances increased the inductive surge in cutting the horn oil also increased and, therefore, the cable insulation had to be relatively heavy to prevent puncturing of the insulation. This made it essential, for good operation, to construct, lay and install special wire and cable equipment and exis ing wires, such as those used by telephone companies could not be used, first, because the conductor size was too small, secondly, because the conductor insulation was in most cases of such a character that it would be doubtful whether it would stand up under the inductive surges referred to and, thirdly, because mixing of the two else as of service (commercial telephone and police signal) was undesirable because these inductive surges would react on the other pairs of commercial telephone conductors in the same cable.

In the present invention, as with my said coponding application, these defects are eliminated by employingan ionized gas lamp across the line as a target or a 'sual signal and by employing a grounded ele tro-r. agnetic horn connected to one side of the l this horn being operated in response to one side of the frequency of the alternating current employed. The use of an ionized lamp eliminates all of the above difiiculties the more particularly in that such a lamp has a definite starting voltage below which it will not function and since this can be made to be more than the vol oi the telephone currents such a lamp can be connected directly across the telephone line circuit without reducing, in any way, the efficiency of speech transmission of the cir cuit. By the selection of a suitable gas, such as neon, for the lamp can also be made to give a distinctive signal which is clearly visible both by day and at night.

The telephone circuit The central station equipment and the several police boxes or substation circuits are connected by the usual telephone lines, each comprising a ring side 10 and a tip side 11. At the police box a telephone receiver 12, hook switch 13 and transmitter 14 are in series with the ring and tip sides of the line circuit. These elements are arranged in the usual manner so that when the receiver 12 is removed from the hook the hook switch 13 closes and an electrical circuit is established between the tip side of the line circuit, transmitter 14, receiver 12 and ring side 10 of the line circuit. Instead, however, of employing the usual mechanical hook switch the hook switch 13 is preferably of the enclosed mercury contact type in which the contacts of the circuit are passed through the sides of a sealed glass found entirely satisfactory in installations made according to the invention.

At the central station the ring side 10 of each line is connected with one armature 15 of the corresponding line signal relay 16. This arn1ature 15 in the normal or de-energized condition of the line relay 16 is in engagement with a con tact 17. This contact 17 is common to all of the line relays l6 and is connected by a common wire 18 with the transmitter and receiver 19 and 20 of the switch board operators telephone set 21. This contact 1'7 is also connected by a common wire 22 with the windings 23 of a line common relay 24. The opposite end of the windings 23 of the line common relay is grounded and is also connected with an armature 25 which in the en ergized condition of the line common relay 24 is held in engagement with a wire 26 which connects with one spring 27 of the cradle switch of the switch board operators telephone set.

The switch board operators set is shown as being of the continental type and the operation of the cradle switch has been represented diagrammatically by continuing the operating plunger of the cradle switch downwardly to engage the spring 27. When the telephone set 21 is placed upon the cradle, the spring contact 2'? of the cradle switch is held in engagement with a spring contact 28, this spring contact 28 being connected to a buzzer 29 and the opposite terminal of this buzzer being connected to a grounded battery B.

The other wire 30 leading to the transmitter and receiver of the switchboard operators telephone set 21 connects with the lower ring contact 31 of the line key 32. Each of these line keys 32 is so arranged that upon throwing the key up the tip spring contact 33 is thrown into engagement with the ring spring contact 31 and a circuit established therebetween. The tip spring contact 33 is connected by a wire 34 with the windings of a line visual signal 35. One of these line visual signals is associated with each line and each comprises the usual electro magnet which, when energized, draws avisual target 36 into the view of the switch board operator through a small window (not shown) so that the operator can identify the particular line calling in. The opposite ends of the line visual signals are connected to a grounded battery 3 lhe wire 34 also connects with a contact 37 which, in the normal or Lie-energized condition of the line relays 16 is engaged by an armature 38. This armature 38 connects directly with the tip side 11 of the line.

Operation of the telephone circuit When the policeman at the police box wishes to talk with the switch board operator he lifts the receiver 12 at the box. This establishes a circuit from battery B through the corresponding line visual signal 35, wire 34, contact 37, armature 38, tip side 11 of the line, transmitter 14, receiver 12, hook switch 13, ring side 19 of the line, armature 15 contact 17, wire 22 and through line common relay 24 to ground. The energization or" the line visual signal 35 draws the target 36' into view so that the switch board operator can identify the particular line circuit calling and the energization of the line common relay 2 draws up its armature 25 so that it contacts with wire 26. As soon as this contact is made a circuit is established from battery B through buzzer 29, springs 28 and 27 of the cradle switch of switch operator's telephone set, wire 26 and armature 25 to ground. This, of course, operates thebuzzer 2% to ground.

29 and calls the attention of the operator to the fact that a call is being made.

The switch board operator then throws up the line key 32 associated with the particular circuit making the call as identified by the line visual and thereby moves the tip and ring spring contacts 33 and 31 into contact With one another. At the same time the switch board operator lifts his telephone set from the cradle switch so that the cradle switch contacts 27 and 28 are moved out of engagement with one another. The opening of thecradle switch of the switch board op erators telephone set causes the buzzer 29 to become inoperative since the grounded end of circuit is broken and the throwing up of the switch key 32 establishes a talking circuit over the line, this talking circuit being fed by battery B This talking circuit is a split circuit, electrical energy being fed from battery B line visual 35, wire 34, contact 37, armature 38, tip side 11 of line, tran mitter 14 and receiver 12, hook switch 13, ring side of line, armature 15 of line signal relay 16, contact 17, wire 22, and windings 23 of line common relay 24 to ground also from battery B through line visual signal 35 over wire 34 through tip and ring spring contacts 33 and 31 of line key 32, wire 36), transin ter and receiver 19 and 26 of switch board operators telephone set 21 wires 18 and 22 and through the windings 23 of line common relay It is therefore apparent that a conversation can be carried on over the telephone circuit as described.

It will be noted that the means for supplying battery to the operators set is not the conventional method used in teiephone practice. The circuit arrangement is such that the operators telephone derives its talking battery from the circuit to which it is connected by means of the line key 32. With the present system the key 32 is also employed to control the sending of signalling energy over the corresponding line as well as to set up the talking circuit between the operator and substations. When the conversation is finished both parties hang up the apparatus thereby being restored to the normal inoperative condition which it had before the patrolman put in his call. When the patrolman hangs up if the switch board operator fails to throw thekey 32 back to normal the buzzer 29 will begin to iuncticn as soon as the operator replaces his telephone set on itscradle switch because the relay 24 is still energized by battery flowing through the operators talking set over a circuit still closed through the springs 31 and 33 of the line key 32. This then provides an alarm circuit notifying the operator that he has failed to restore the key to its normal inoperative position.

The signalling circuit Associated with each box is arranged an audible signal comprising an electric horn .0 and a visual signal 41, these two signals being so arranged as to be visible and audibl at a distance from the box, their purpose being to call the patrolman to the box in order to give him instrucdirectly converted into sound energy, has the effect of creating a sounding pitch of double the frequency of the electrical energy due to the fact that the negative electrical impulse creates one sound impulse and thepositive electrical impulse creates another sound impulse and since one cycle consists of one negative and one positive impulse, one cycle in the frequency of the electrical energy creates two sound impulses of the same character. The horn 49 is connected by a wire 42 to the ring side of the line andits other terminal is gounded. The visual signal a1 is connected across the line by wires 4. 3 and 44. This is possible in the present system since the signal 41 is not a filament lamp but is an ionized gas type lamp. In my said copending application, Serial No. 525,471, filed March 26, 1931, I have described a type of lamp or visual target which is particularly suited for the purpose and in general this target consists of a lamp having the conventional Edison base and carrying a clear glass globe 45 which is hermetically sealed to the base and is filled with a gas to obtain the desired color. Neon gas is the best suited for the present use since it gives a color approaching the red heretofore used as visual. signal in systems of this character and forms a distinctive target. Withthe globe 15 are arranged a pair of spaced electrodes 46, each of which is connected to one of the wires 43 and 4M. When a current of high enough voltage is impressed upon the electrodes 46 the lamp is illuminated to give a distinctive colored light which is easily discernible both at day and at night. 4 The starting voltage of this lamp is, however, higher than the normal voltages of the talking currents and hence when such a lamp is placed across a circuit having a lower voltage than is necessary to ionize the lamp, in other words, the starting voltage, the lamp has the characteristics of capacity said circuit. Inasmuch as the size of the two electrodes is relat y small and the spacing between them is relatively large, the capacity effect will be exv ccedingly low on talking frequencies and the losses to said talking frequencies through the shunt circuit formed by the lamp would be negligible. Furthermore, at no time would there be any battery leakage through said lamp. Therefore it is not necessary to incorporate a condenser in with said lamp across said circuit for the purpose of blocking the battery current. This then makes 'an'icleal signalling and talking circuit because the lamp itself can work under its highest ei'liciency on the signal current used, creates no loss to the talking frequencies of the telephone circuit and acts as a condenser, blocking oil" the flow of battery current from. one side of the line circuit to the other.

The source of alternating current for the oper ation of the visual and audible signals at the police boxes comprises a motor 4'? directly connested with a generator 48 and the generator shaft 19 through a train of gears (not shown) drives the flasher contact shaft 50, this flasher contact shaft 56 carrying the contacts of a flasher. One terminal of the motor a7 is connected to one commercial power line 51 usually supply- 66 cycle current llilvolts and the other motor terminal is connected to the other commercial power line 52 through a wire 53, spring contact 5% of a power key 55, and a second spring contact 56 of this same key 55. The key carries a second set of spring contacts 57 and 58 and the spring contacts 58 and 56 are arranged to work in unison and both close with their corresponding contacts 5'7 and 54 upon throwing the key 55 down. The spring contact 58 is connected with a grounded battery B and its corresponding spring contact 57 is connected by a wire 59 with a primary flasher contact 60 on the flasher contact shaft 50. This primary flash- .er contact 60 is metallic and is in the form of an extended cam which on each revolution of the flasher shaft 50 engages a contact finger 61. This contact finger 61 is connected by a common wire 62 with one of the upper contact springs 63 of the line key 32 and when this line key is thrown down this spring contact 63 is engaged by a second spring contact 64. The spring contact 64 is connected by a wire 65 with the windings 66 of the corresponding line signal relay 16 and the other ends of the windings 66 of all of the line signal relays 16 connected by a common wire with a fixed contact 67. This contact, in the normal or (lo-energized condition of the line common relay 24 is engaged by the grounded armature 25. The flasher includes a secondary flasher contact cam 68 which is also mounted on the flasher contact shaft 50 adjacent the primary rotary flasher contact 60. The secondary contact is also in the form of a metal cam but is shorter in its effective length than the primary flasher contact 60, the primary flasher contact 60 acting, through battery current, to set up the circuit for signalling and the secondary flasher contact 68 sending generator current over the set up circuit. By setting up and breaking the signalling circuit in advance of sending generator current over it or cutting off the generator current (by the larger size of the primary flasher contact 60) arcing of the contacts on the line signal relays 16 is avoided.

The secondary rotary flasher contact 68 is continuously connected by a wire 69 with the central spring contact '70 of a key 71. This key 71 is a non-holding key and upon being released immediately assumes its normal position shown, in which the central spring contact engages a spring contact 72 and is outof engagement with a spring contact 73. The spring contact '73 is grounded and the spring contact 72 is connected by a com mon wire 74 with contacts 75 of all line signal relays 16, these contacts '75 being engaged by the armatures 38 of the line signal relays 16 on such line signal relays 16 as may be energized.

The secondary rotary flasher contact 68 contact-s with a contact finger 76 which. is connected by a wire '77 with one terminal of the 110 volt, 150 cycle generator 48. The other terminal of this generator is connected by a common wire 78 with contacts 79 of all. of the line signal relays 16, these contacts 79 being engaged by their armatures 15 on such line signal relays as are energized.

Operation ofthc signal circuit When the switch board operator wishes to call a patrolman to his box to give him instructions the operator throws the master key 55 down and also throws down the line key 32 on such lines as he desires to use. This establishes contact between the corresponding spring contacts 63 and 6 1; 54 and 56; and 57 and 58. The motor i7 is thereby energized from the commercial power line 51, motor 4'7, wire 53, closed spring contacts 54 and 56 of key 55 and commercial power line 52. The energization of the motor starts the rotation of the generator shaft 49 which drives the primary rotary flasher contact 60 and the rotation of this primary flasher contact 60 operates to set up periodically the signalling circuit for sending signalling impulses over the particular line circuits selected. In so setting up the line circuits over which the signal impulses are to be sent, the current from battery B passes through the closed spring contacts 58 and 57 of key 55, wire 59, primary flasher contact 60, contact finger 61, common wire d2, closed spring contact fingers 63 and 6a of the set-up line keys 32, corresponding wires wind s 56 of the corresponding line sign-l relays 16, wire and contact 6'7 and armature 25 to ground. The energization of the line relays 16 draws up their armatures 15 and 38, thereby disconnecting the entire tall-ring circuit and setting up the signalling circuit.

The rotation of the generator shaft 49 operates the generator 48 and also rotates the secondary rotary flasher contact 68. When this occurs 159 cycle current of 110 volts flows from the generator 43, wire .77, contact finger '76, secondary rotary flasher contact 68, wire 69, closed spring contacts '70 and '72 of key '71, wire '74, contacts 75, armatures 38 of the energized line relays 16, tip sides 11 or" lines, wires 43, ionized gas lamp 41, wires 44, ring sides 10 of the set up lines, armatures 15 of the energized relays 16, contacts '79 and wire '78 to the other terminal of the generator. Each time the flasher contact shaft rota es it sets up the signalling circuit through the primary rotary flasher contact and subsequently sends out a signalling impulse over the set up circuits through the visual signals 41. The visual signal lights 41 of the setup circuits, therefore, flash on and oil periodically until the patro inan answers the call.

The visual signal 41 at the boxis not always within view of the patrolman and it is therefore necessary to give a few blasts on the horn 40 to call his attention to the fact that he is wanted at the This cannot, however, be continued. as the periodic blast of the horn or howler is extremely annoying to the residents near the box if its operation is continued for any su stantial period of time. To give a few blasts on the horn the operator throws down the non-holding key for a short time and then releases it to its normal position shown. In so doing he breaks the contact between the spring contacts 72 and '70 and establishes it between the spring contacts '70 and 73. When this is done a circuit of 150 cycle current is established. through ground, spring contacts '73 and '70 of key '71, wire 69, secondary flasher contact 68, contact '76, wire 7?, generator 48, wire '78, contacts '79, armatures 15 of the energized relays 16 of the set up circuits, ring sides 10 of lines, wires a2 and horns 40 to ground. When the desired number of blasts have been given the operator releases the key '71 and the periodic operation of the visual signal 41 is resumed until he policeman answers the call.

The use of the master key '71 for changing from visual to audible signals over one or more line circuits is covered by my Patent No. 1,797,281, dated March 1931.

It will be noted that during the signalling intervals line relays 16 break oil the normal talking circuits and equipment at the central station. This is purposely done to prevent the high voltage current from backing up through any of this apparatus. However, during this interval this equipment cannot function. Therefore, when a patrolman answers during the signalling interval he cannot reach the central station. However, as the signalling intervals are purposely made to extend over a period of one-half second and as the silent intervals are of approximately the same length these non-operative intervals of the talking circuit are merely momentary and have no effect on the operation of the system. Thus between each signalling period the line relays of the set up circuits are in their normal non operative positions and as soon as the patrolman lifts the receiver a circuit is established, at the first non-signalling interval, through battery 13 line visual 35, wire 34, contact 3'7, armature 38 or" the then de-energized line relays 1'6, tip side ll of line, transmitter 14, receiver 12, hook switch 13, ring side 10 of line, armature 15 of the same tie-energized line relay 16, contact 17, wire 22 and through winding 23 of line common relay 2% to ground. This energizes the line common relay 24 and thereby breaks the grounded contact 25 with the contact 6'7 and thereby breaks the grounded side of the circuits of all of the line relays 16 at contact 67, thereby preventing the further operation of any of the line relays 16 tosend out more signalling impulses over any lines and establishing the normal talking circuit on the answering line as previously described.

The substitution of the ionized type of lamp 41 for the usual tungsten filament type of I lamp provides the desired colored lamp necessary for police signal work. It was also discovered in experimental work that such a lamp made to operate at 110 volts has an entirely different re-action to lower voltage than a tungsten filament lamp. In the filament type of lamp, the lamp has a definite resistance which varies according to temperature but a current of any voltage will flow through the filament. With the ionized gas lamp, the gas does not become a conductor until a voltage has been reached which will ionize the gas between the two electrodes. In the lamp used in the present case, this cutting-01f point should be around 40 volts or higher because the direct current voltages used do not exceed 24 volts. This results in such a lamp being a completely open circuit for any current whose voltage does not exceed the initial starting voltage required by the lamp. Therefore with a lamp of this type it is possible, as shown, to connect .it directly across the talking circuit and the only loss of talking energy is the effect of the two electrodes acting as a condenser.

The capacity of the lamp as a condenser is so low as to have no measurable eifect in absorption of the talking energy. With the present system, therefore, I am enabled to place the lamp directly across the talking circuit without any effect on the talking currents and at the same time completely block off the flow of the relatively low voltage battery current through the lamp. With the filament type of lamp it would be necessary to include a condenser in the lamp circuit to obtain the same result. Inasmuch as the capacity reaction of a lamp is exceedingly small there are no surge effects upon the line.

By the elimination of a colored globe over the lamp 41 a loss of over 89% of the total energy of the light in passing through this filter permits of the use of a five watt ionized gas type of lamp in place of the fifteen watt tungsten filament lamp formerly required. With the drop of fifteen watts of energy to five watts a gain is made in filament and the elimination of the red filter.

erators set to the line.

However, with the horn the area over which it will be heard is restricted and as it is desirable to use the energy consumption in the horn as in the lamp, in the present installation, advantage is taken of the fact that as'the pitch of the sound is increased the amount of energy necessary to cause it to cover the same area can be decreased. Thereiora it is desirable to use a current source having a frequency of approximately 156 cycles or higher, which frequency will operate to advantage both with the lamp and the horn. With the lamp only one electrode is illuminated at a time and only during that part of the voltage Wave or curve above the initial ionization point so that the lamp is fully illuminated only one-fourth of the time so that with 150 cycle current these impulses come much closer together and the over-all illuminated effect is much better than at low frequency periods. With the electro-magnetic type of horn the sound frequency is double the electrical frequency as previously pointed out, so that with 150 cycle current 309 sound impulses per second are produced, which is sufficiently high pitched to cover the desired area even though the horn operates with less electrical energy.

When the horn is being used it is connected from oneside of the line to ground and this particular part of the circuit then acts as one side of a condenser, the size of the condenser varying as the length of the circuit. There would normally occur, therefore, at each cutting-01f point of the horn an inductive reaction back through the circuit which is not desirable. However, the lamp 61 across the line acts as an automatic drain for the surges and comes into action instantaneously for any voltages above the ionizing voltage required to start the lamp. Inasmuch as this Voltage lies, say, between 40 and volts and the horn operating voltage is 110 volts there can be no disturbing surges occurring within the system since the instantaneous reaction of the lamp to high voltages drains such voltages so that they have no harmful effects on any parts of the circuit.

The present circuit is a great deal simpler and'less expensive both to install and maintain than the circuit described in my said co-pending application, Serial No. 525,471, of March 26, 1931. In said previous application the switch board equipment consisted of two lamp signals and a signal key associated with each line circuit. In addition to this there was also a line relay (22) for each line. In the new circuit, for the sake oi simplicity, and economy of construction, the visual signal 35 is used in place of the line lamp i-G) of the former circuit. This makes possible to dispense with the line relay 22 of the former circuit and its group of three contacts for each line circuit and use only one such line relay common to all of the circuits in the system. The signal key 20 in the former circuit contained two groups of springs, one group of two springs for operating the line signals and one group of six springs, two of which were used for cutting-off the line relays ll) and the other four for connecting the operators talking set with the line. In the present circuit this line key 32 has only two groups of two springs each, one group, as in the other circuit for operating the line signals and the other pair of springs for connecting the op- In the former circuit when a group of signals were in operation and anyone answered from one of these lines he would shut off the signals in that line only and the signals on the remaining lines would still continue to function. In the new circuit, due to the use of only one relay 24, common to all of the lines, as soon as a party answers, the sig nals on all of the other lines stop functioning until this circuit has been restored to a nontalking condition when the signals automatically continue to operate on the other circuits.

In the new circuit, therefore, a large amount of contacts and apparatus necessary to the older circuit have been eliminated. While the present circuit is not so flexible in some respects as the other type, for small units it is equally as efiicient and would have the advantage of lower first cost and lower maintenance. The first cost would not only come with the saving of the apparatus referred to but will also come because it will operate on a much smaller battery output under full load. To illustrate, in the former circuit,

when signals were set up, the telltale light 95 was operated on each line. This, in connection with the signal relays 16 required sufiicient battery so that on a system oi 40 to 50 lines the energy consumption was so high that a relatively large sized battery had to be used to offset the intermittent voltage drops that some on during the flashing periods when the maximum current is being used. In the new type of circuit this extra strain is eliminated and inasmuch as the signal part of the circuit cannot function during the period that conversation is being carried on over any one circuit the voltage drop during operat ing conditions as above described cannot exist during a period when telephone conversation is being held over any circuit. We then have an arrangement in which. it is possible to dispense with storage batteries entirely or to use relatively small capacity batteries. If batteries are di" pensed with it is then necessary to use a filtered direct current produced by any one of the sov eral makes of A. C. rectifiers for this purpose. The amount of filtration of said current need not be very great as the signal relays themselves can be operated on a current with very little f1ltration as long as the voltage remains sufficiently high and a much larger amount of voltage drop can be permitted with this arrangement than in the other circuit where the switch board lamps 40 and 95 were used, as the brilliancy of their signals was in proportion to the battery current and also the interruptions caused by the intermittent operations of the line signal relays l6 and their associated tell-tale lamps required a relatively large battery so that voltage fluctuations were held at a minimum to prevent interference with telephone conversations carried on while signals on other lines were in operation.

While I have shown one embodiment of the invention it is apparent that the essential features of the invention can be embodied in the systems of widely different character and the invention is, therefore, not to be considered as limited to any particular form but the invention is to be accorded the full scope comprehended by the accompanying claims.

Under certain physical conditions of operation it may be desirable, in some instances, to place more than one substation on a circuit and such arrangement is comprehended by the appended claims.

I claim as my invention:

1. In combination with a common battery telephone system, comprising a central station switchboard, a plurality of substations and a Cir line circuit connecting each of said substations with said switchboard, said line circuits being normally impressed with said common battery telephone current; a substation telephone set in each line circuit, a substation signal device connected to its respective line circuit and actuated by current having a voltage in excess of that of said common battery, a switchboard operators telephone set, a line circuit switching key associated with each line circuit at said switchboard and adapted to connect said switchboard operators telephone set with any of said line circuits, a common relay having its windings common to one side of all of said iine circuits and also common to one side of said switchboard operators telephone set, said common relay be ing energized through any circuit change which permits battery to flow through any of said line circuits, a source of signal energy having a voltage in excess or said common battery for the operation of said signal devices, means for connecting said line circuits with said source of signal energy and means actuated through the energization of said common relay for cutting off the supply of signal energy to all of said line circuits and thereby rendering all signal devices in the system inoperative.

2. In combination with a common battery telephone system, comprising a central station switchboard, a plurality of substations and a line circuit connecting each of said substations with said switchboard, said line circuits being normally impressed with said common battery telephone current; a substation telephone set in each line circuit, a substation signal device connected to its respective line circuit and actuated by current having a voltage in excess or that of said common battery, a switchboard operators telephone set, a line circuit switching key associated with each circuit at said switchboard and adapted to connect said switchboard operators telephone set with any of said line circuits, a common relay having its windings common to one'side of all of said line circuits and also common to said switchboard operators telephone set, said common relay beingenergized through any circuit change which permits battery to flow through any of said line circuits, a source of signal energy having a voltage in excess of said common battery for the operation of said signal devices, and means for estab shing a signal circuit from said source of signal energy through each of said line circuits including a contact and the armature of said common relay engaging said contact, the energization of said common relay effecting a breaking of the contact between saidarmature and its contact and thereby cutting off the supply of signal energy to all of said line circuits.

3. In combination with a common battery telephone system, comprising a central station switchboard, a plurality of substations and a line circuit connecting each of said substations with said switchboard, said line circuits being normally impressed with said common battery telephone current; a substation telephone set in each line circuit, a substation signal device connected to its respective line circuit and actuated by current having a voltage in excess of that of said common battery, a switchboard operators telephone set, a talking switch associated with each line circuit at said switchboard and adapted to connect said switchboard operators telephone 'set with any of said line circuits, a common relay having its windings common to-one side of all of said line circuits and also common to said switchboard operators telephone set, said common relay being energized through any circuit change which permits battery to flow through any of said line circuits, a source of signal energy having a voltage in excess of that of said common battery, a signal switch associated with each line circuit at said switchboard and adapted to connect said source of signal energy with any of said line circuits for the operation of the corresponding signal devices, the return circuit of said signal energy including the armature of said common relay and a contact engaged by said armature when said common relay is deenergized, the energization of said common relay thereby breaking the return circuit to said source of signal energy and deenergizing all signal devices on all line circuits.

A common battery telephone system, comprising a central station switchboard, a plurality of substations, a line circuit connecting each or" said substations with said central station switchboard, a line visual signal at the switchboard connected to one side of each of said line circuits," the other side of said line circuits being commoned, a common line relay in the com moned side or" said line circuits, a switchboard operators telephone set, a line circuit switch key at the switchboard associated with each line circuit and having contact arrangements to connect the operators telephone set across the line circuit of any one line circuit and means for supplying the battery current to the operators telephone set through the windings of said line relay common to all line circuits and also supplying said battery current through the windings of the line visual signal of the circuit to which the operators telephone set may be connected.

5. A common battery telephone system, comprising a central station switchboard, a plurality of substations, a line circuit connecting each of said substations with said switchboard, a switchboard line visual signal connected with one side of each of said line circuits and being the impedance through which the battery is sup plied to all of said line' circuits, the other side of said line circuits being commoned, a switch board operators telephone set having one side connected to the commoned side of said line circuits, a talking key for each line circuit and adapted to connect said switchboard operators telephone set with the other side of each line circuit, and a line common relay having a grounded armature adapted, when said relay is energized, to engage a contact of the commoned side of said line circuits, said armature being connected to, the windings of said common relay and said windings being also in circuit with the commoned side of said line circuits, said line common relay thereby being the impedance for the line circuits on the grounded side of the battery and also being en rgized to set up a talking circuit on lifting the receiver any substation telephone set.

6. A common battery telephone system, comprising a central station switchboard, a plurality of substations, a line circuit connecting each of said substations with said switchboard, a switchboard line visual signal connected with one side of each of said line circuits and being the impedance through which the battery is supplied to all of said line circuits, the other side of said line circuits being ccmmoned, a switchboard operators telephone having one side connected .to the commoned side of said line =ircuits, a talking key for each line circuit and adapted to connect said switchboard operators telephone set with the other side of each line circuit, a line common relay having a grounded armature, adapted, when said relay is encrgized, to engage a contact of the commoned side of said line circuits, said armature being connected to the windings of said common relay and said windings being also in circuit with the commoned side of said line circuits, said line common relay thereby being the impedance ior the line circuits on the grounded side of the battery and also being energized to set up a talking circuit on lifting the receiver at any substation telephone set, and a buzzer having one terminal connected to the cradle switch of the operators telephone set and its other terminal connected to battery whereby when saidcommon relay is energized and said cradle switch is closed, a circuit is established from battery through said buzzer, cradle switch, commoned side of line circuits, common contact and armature to ground.

7. In combination with a common battery telephone system, comprising a central station switchboard, a plurality of substations and a line circuit connecting each of said substations with said switchboard; a substation telephone set in each line circuit, a substation signal device connected to each line circuit and actuated by current having a voltage in excess of that of said common battery, a switchboard line visual signal connected with one side of each of said line circuits and being the impedance through which the battery is supplied to all of said line circuits, the other side of said lino circuits being commoned, a switchboard operators telephone set having one side connected to the commoned side of said line circuits, a line circuit switching key associated with each line circuit at said switchboard and adapted to connect said switchboard operators telephone set with the other side oi" each line circuit, a line common relay having a grounded armature adapted, when said common relay is energized, to engage a contact of the commoned side of said line circuits, said armature being connected to the windings of said common relay and said windings being also in circuit with the commoned side of said line circuits, said line common relay thereby being the impedance for the line circuits onthe grounded side of the battery and also being energized through any circuit change which permits battery to flow through any of said line circuits, a source of signal energy having a voltage in excess of said common battery for the operation of said signal devices, means for connecting said line circuits with said source of signal energy and means, including a contact engaged by said armature when said line common relay is deenergized, for cutting off the supply of signal energy to all of said line circuits and thereby rendering all of said signal devices in the system inoperative upon establishing a talking circuit.

8. In combination with a common battery telephone system, comprising a central station switchboard, a plurality of substations and a line circuit connecting each of said substations with said switchboard, said line circuits being normally impressed with said common battery telephone current and one side of said line circuit being commoned; a substation telephone set in each line circuit, a substation signal device connected to each line circuit and actuated by current having a voltage in excess of that of said common battery, an operators telephone set having one side connected with the commoned side of said line circuits, a line circuit switching key associated with each line circuit at said switchboard and adapted to connect the other side of each line circuit with said operators telephone set, a line signal relay associated with each line circuit and each in its normal deenergized condition establishing he talking circuit between the operators telephone set and the corr sponding substation telephone set, a source of signal energy for the operation or said signal devices, means connecting said source of signal energy with said line signal relays whereby when any of said relays is energized, signal energy is sent over the corresponding lines for the operation of said signal devices, manual means for selectively energizing said line signal relays, a line common relay in the commoned side of said line circuits and energized by said common battery when a battery circuit is established in any of said line circuits, and means actuated through the energization of said line common relay for deenergizing all of said line signal relays and thereby cutting off the supply of signal energy to all of said signal devices following any ci'cuit change which permits battery to flow through any of said line circuits.

9. In combination with a common battery telephone system, comprising a central station switchboard, a plurality of substations and a line circuit connecting each of said substations with switchboard, said line circuits being normally impressed with said common battery telephone current and one side or said line circuits being commoned; a substation telephone set in each. line circuit, a substation signal device connectcd across each line circuit, each of said signal devices forming a completely open circuit across its line circuit at the voltages of said common battery, an operators telephone set having one side connected with the commoned side of said line circuits, a line circuit switching key associated with each line circuit for connecting the other side of each line circuit with said opcrators telephone set, a line signal relay associated with each line circuit and each in its normal deenergized condition completing the talking circuit between the operators telephone set and the corresponding substation telephone a source of intermittent alternating current for the operation of said signal devices, means connecting said source of signal current with said line signal relays whereby when any of said relays are energized signal energy is sent over the corresponding lines for the operation 01" said signal devices, manual means for selectively energizing said line signal relays, a line common relay in the commoned side of said line circuits and energized by said common battery through any circuit change which permits battery to flow through any of saidline, circuits, and means actuated through the energization of said line common relay for deenergizing all of said a line signal relays and thereby cutting off the sup- I ply of signal energy to all of said signal devices.

10.111 combination with a common battery telephone system, comprising a central station switchboard, a plurality of substations and a line circuit connecting each of substations with said switchboard, said line circuits being normally impressed with said common battery tele-- phone current and one side of said line circuits being commoned; a substation telephone set in each line circuit, a substation signal device connect'ed across each line circuit, each of said sig- 7 nal devices comprising an ionized gas signal lamp connected across each line circuit at the corresponding substation and forming a completely open circuit across its line circuit at the'voltages of said common battery, an operators telephone set having one side connected with the commoned side of said line circuits, a line circuit switching key associated with each line circuit for connecting the other side of each line, circuit with said operator's telephone set, a line signal relay associated with each line circuit and each in its normal deenergized condition completingv the talking circuit between the operators telephone set and the corresponding substation telephone set, a source of intermittent alternating current for the operation of saidcsignal devices,.

said line signal relays and thereby cutting off the supply or signal energy to all of said signal devices.

GUSTAV F. C. BAUER. 

